Aspects of the present invention relate to lighting, and more particularly to an optical element including texturing to control beam width and color mixing of light from a lighting device.
Light emitting diodes (LEDs) are finding more and more applications in general lighting as a result of the increase in efficiency of LEDs. Because of the semiconductor bandgap nature of LEDs as a light source, LEDs can provide a wide range of color by either a single color LED or by mixing the light from several LEDs of different colors. One example is the True White technology, which combines a blue shifted yellow (BSY) and red LED in proper lumen proportion to achieve high efficacy white color light with a high color rendering index (CRI). For multi-color LED lighting, providing well mixed color is challenging. Uniform color mixing in directional LED lighting applications can also present difficulties.
Typically the angular distribution of light emitted from an LED is close to Lambertian, which has a full width at half maximum (FWHM) beam angle of 120 degrees. Directional LED lighting preferably has a narrower beam angle, such as about 12 degrees, about 25 degrees, or about 40 degrees, or other angles depending on the application. The collimation of the light is usually realized by a reflector or a total internal reflector (TIR). With multi-color LEDs, the light leaving the reflector or TIR optics are usually not well mixed and sometimes the beam profile is not smooth enough. The beam profile being smooth may be defined as the footprint of a beam of light on a surface not having a patchy appearance or the brightness of the beam not being patchy or irregular within the beam footprint or beam profile.